Remote missile command system



Jan. 30, 1968 w. B. M KNIGHT ETAL 3,366,346

REMOTE MISSILE COMMAND SYSTEM Filed July 19, 1965 3 Sheets-Sheet 2 I IMISSILE MISSILE DETECTOR FM DYNAMICS TRACKING UNIT AMPLIFIER DEMODULATORREFERENCE SIGNAL COMPARISON AMPLIFIER NETWORK 3| A IMITII NEL z CHANBIAS COMMANO ERROR COOER TRANSt-ATOR /I IMITER ELEVATION CHANNEL RCOMMAND ERROR CODER TRANSLATOR/ LIMITER I FIG. 2

AMPLITUDE I ERROR v 50 4O 3O 20 IO 0 IO 20 3o 40 5o ANGLEW'LS) 0.0 VOLTSFREQUENCY 6 -Wi||i m B. McKni hf LOnnIe N. McClus y Nicholas J. MOn usINVE TORS.

w. B. M KNIGHT ETAL REMOTE MISSILE COMMAND SYSTEM Jan. 30; 1968 3Sheets-Sheet Filed July 19, 1965 Lonnie N. McClus y Nicholas J. MongusINVENTORS.

BY W J, Wail United States Patent 3,366,346 REMGTE MISSILE EOM'MANDSYSTEM William B. McKnight, Somerville, Lonnie N. McClusky,

Torrey, and Nicholas J. l /iangus, Huntsville, Ala, as-

signors to the United States of America as represented by the Secretaryof the Army Filed July 19, 1965, Ser. No. 473,572 3 Claims. (Cl.244-311) The invention described herein may be manufactured and used byor for the Government for governmental purposes without the payment ofany royalty thereon.

This invention relates generally to a system for guiding missiles to atarget which has been acquired and sighted by visual or other means.More particularly the present invention relates to an infrared detectorwhich senses the line-of-sight of a missile launched at a selectedtarget, and provides signals indicating errors of the missileline-ofsight compared with its own line-of-sight. The line-ofsight ofthe detector is centered by an operator on the target, most likely atank.

In the field of command guidance of air-to-ground or ground-to-groundmissiles primarily for use against tanks, at number of problems arepresented by a system of visual missile tracking. Manual operation ofcontrols that guide self-propelled missiles to the target require ahighly skilled, highly trained operator. Even so, the reflexes of a manare very often too slow to hit a moving target. Due to these slowreflexes, the missile used has to be a slow speed one. Further, theeyesight of a man, unaided, is insufiicient when the target is at a fardistance. If he uses an optical device, he will have difiiculty inacquiring both the missile and the target in his field of view at thesame time especially just after firing of the missile. If he tries toovercome this by using unaided eyesight at first to get the missile inline with the target and then switch to an optical device, there will bea time, when he is changing to the optical device and bringing it tosight on the missile that the missile is not under control. This isobviously undesirable.

It is therefore an object of this invention to provide a missileguidance system which requires a minimum of skill for the operator.

A further object of the present invention is to provide a guidancesystem in which the operator may at all times use an optical aid.

A still further object of the invention is to use an automatic infraredguidance system in combination with manual control to acheive highaccuracy guidance.

In the field of command guidance of air-to-ground and ground-to-groundmissiles which are primarily used against tanks, a number ofimprovements over manual missile tracking are provided by an infraredmissile tracker which furnished error signals to the missile andmaintains it on a direct line-of-sight. Infrared automatic commandguidance allows the use of relatively high speed missiles, and overcomesthe loss of missiles resulting from inadequate manual guidance. The useof this invention allows the unskilled operator to successfully hit thetarget, as the operator is only required to center an optical sight onthe target and pull the trigger.

The invention further resides in and is characterized by various novelfeatures of construction, combinations, and arrangements of parts whichare pointed out with particularity in the claims annexed to and forminga part of this specification. Complete understanding of the inventionand an introduction to other objects and features not specificallymentioned will be apparent to those skilled in the art to which itpertains when reference is made to the following detailed description ofa specific embodiment thereof and read in conjunction with the appendeddrawing. The drawing, which forms a part of the specification,

presents the same reference characters to represent correspending andlike parts throughout the drawing, and wherein:

FIGURE '1 shows a pictorial representation of the semiautomatic infraredcommand system according to the invention;

FIGURE 2 illustrates a system in block diagram in accordance to theinvention;

FIGURE 3 is a graph of the relative control signal vs. the error angleor the target;

FIGURE 4 illustrates a cut away view of the missile tracking unit of thepresent invention showing only front lines;

FIGURE 5 shows the design of the reticle pattern used in this invention,and

FIGURE 6 illustrates the relationship of the input to the output of theFM demodulator wherein the abscissa is the input in frequency and theordinate is the output in volts.

In order to better understand the operation of the system described inthe figures a description of their components referred to is firstpresented. FIGURE 1, which is a pictorial representation of thesemiautomatic system, shows a missile 1 in flight heading toward thetarget 3 which is a tank. An infrared source 4 (such as sodium flare) isattached to the missile. Missile is guided by signals from the commandunit 5. The missile is shown to be a wire guided missile but may use anyof the well known command guided missiles. Likewise, the outputcircuitry of the command unit may be the input of the well known commandlinks. A launcher 7 is shown and may be of any desired design. More thanone missile may be provided and there also may be more than onelauncher.

The output and the fire circuitry of command unit 5 is controlled by thecontrol assembly 9. The control assembly comprises a trigger 11 whichcontrols the fire circuit, a missile tracking unit 13 which providestracking signals, a telescope 15 which provides a means to sight, and astock 17 which provides support for the assembly. Telescope 1S and unit13 have their axes in alignment, insofar as sighting on a distant targetis concerned.

In FIGURE 2 the missile tracking unit 13 is shown as having its outputconnected to an input of an infrared detector amplifier 21. The outputof amplifier Z1 is connected to the input of the F M demodulator 23whose output is one of the inputs of comparison network 25. The otherinput of network 25 is the reference signal amplifier 27. A scan drivepower unit 29 is provided for unit 13.

Comparison net work 25 has control signal outputs 86 and 87 which areadded with bias means 31 and 32 sent to the azimuth and elevationchannels. The azimuth and elevation channels each contain an errortranslator limiter 34 and 3S and a command coder 37 and 38. The outputsof the command coders are coupled either by wire or wireless to themissile dynamics 40, for guiding the missile. FIGURE 3 shows the plot ofthe relative control signal output of the phase comparison networkagainst the error in angle of the missile.

FIGURE 4 shows a cut away view of the missile tracking unit 13. Thisunit is a modified cassegrain optical system (folded telescope). Acasing 43 encircles the components of the device. Infrared radiationfrom source Al on the missile enters the front of the device throughcorrecting lens 45, reflects off the primary mirror 47 to the secondarymirror 49 and passes on to a reticle 51. The reticle is in the focalplane of mirror 49. The radiation energy passes through reticle 51,field lens 53, and lens 55' to an immersed IR detector 57. The output ofdetector 5'7 is connected to amplifier 21 by way of cable 66.

Secondary mirror 49 is mounted for rotation by the shaft 63 of the motordrive of unit 65. Mirror 49 is not mounted at a 90 angle with respect toshaft 63, but is skewed with respect thereto. Sun baffles 67 are blackgrooves cut in the structure to trap stray radiation, especially fromthe sun. Motor drive and reference signal generator 65 has a generatorwhich is driven by the motor. Suitable optical filters may be providedat the front of casing 43 at/or in the correcting lens 45 for filteringout all the radiation except the infrared radiation to be detected.

FIGURE shows a reticle 51 for chopping the infrared energy which isfocused thereon. Reticle 51 is a disc-like structure and may be of anydesired configuration. A suitable form of the reticle of this inventioncomprises a plurality of alternate pie shaped opaque portions 70 andtranslucent portions 71, with respect to the radiant energy to bedetectedin this case infrared energy. By translucent is meant theability to transmit the waves of the radiant energy to be received. Aquartz glass may be used for the reticle of this invention.

Operation The operator 75 (FIGURE 1) sights a target 3 and determineswhich missile can be fired so as to come in sight of the detector 13. Hethen sets the controls on command unit 5 so as to select the propermissile (only one missile is shown in FIGURE 1) and to provide anyneeded bias. Operator 75 now sights on the target through telescope 15,pulls the trigger 11, and continues to keep the target within thetelescopes cross-hairs until the missile 1 impacts against the target.The operator now may select another target and repeat the operation.

After trigger 11 is depressed command unit 5 causes the selected missileto be launched, and its infrared source to start emitting. Infraredradiation emitted from the source on the selected missile entersdetector 13 by Way of the correction lens 45. This radiation isreflected by primary mirror 47 to skewed mirror 49 and is focused ontoreticle 51. It is passed through reticle 51 and a field lens 53 and isrefocused to an immersed IR de tector 57. The rotation of the motor ofunit 65 causes the image of a point in the field of view to describe acircle in the focal plane. The reticle is located in. this focal plane.The reticle, therefore, chops the infrared energy and causes IR detector57 to have an alternating current output. If the image (this being theinfrared source 4 which is affixed to the missile) is centered on theaixs of detector 13, the circle will be centered on the reticle and willcause an output of IR detector 57 which represents a carrier signalfrequency. However, if the missile is off axis, the circle will nolonger be centered on the reticle (see dotted circle 84 of FIGURE 5) andwill cause a frequency deviation in the carrier signal.

The output of detector 57 is amplified by IR detector amplifier 21(FIGURE 2) and then sent to FM demodulator 23 where, after demodulationand filtering, the frequency deviation of the carrier signal isrepresented by a signal output 82. The function of demodulator 23 isshown by FIGURE 6 wherein the abscissa is the input signal frequency andthe ordinate is the output 82 of the demodulator. Signal output 82 isequal to the frequency of the reference signal generator output of unit65 which is the r.p.s. of the mirror 49. It can easily be seen fromFIGURES 5 and 6 that the phase of signal 82 will change with respect tothe polar angle of the center of circle 84; therefore the polar angle,with respect to the axis of detector 13, of the missile can be equatedto the phase of signal 82-. Once the phase of the reference signal withrespect to the position of the mirror 49 is set, then a comparisonnetwork 25 can compare these two signals in phase and produce controlsignal outputs 86 and 87 which are proportioned so as to indicate thepolar error angle in X and Y coordinates. The amplitude of signal 82,therefore, can be converted into control signals 86 and 87 with respectto the error angle function as shown in FIGURE 3. The reason theamplitude falls off after an angle error of more than 10 milsnotindicated by FIG- URE 6is that the circle 84 on the reticle will nolonger encircle the center of the reticle at such an error angle.However, even if circle 84 made by the image does not inclose the centerof the reticle, the phase of signal 82 will still give a true indicationof the polar angle. This is because even if circle 84 were to be abovecenter, the bottom of circle will still have the highest frequency andthe top will still have the lowest. Since this usually happens only justafter the launching of the missile, the missile has suflicient time,even with minimum guidance, to come into line with detector 13.

Comparison network 25 compares signal 82 with the reference signal 28 inboth phase and amplitude and produces control signal outputs 86 and 87representative of X-Y coordinates. Signal 86 indicates azimuth (left orright) information, and signal 87 indicates elevation information. Thesesignals are sent to the azimuth channel and the elevation channelrespectively. Biases 31 and 32 may be added to these signals toinitially guide the missile to a position in the field of view of thedetector 13. Bias 32 may also be used to compensate for the gravitationpull on the missile by adding a constant down error component to signal87. The azimuth and elevation channels translate and limit their inputsinto error position of the missile, and their command coders 37 and 38code this information and send it on to the missile. In this specificembodiment a wire guided missile is shown and the coded signals would besent along the wires 90 (FIGURE 1) to the missile 1. However any commandguided missile may be used, such as electromagnetic radiation guidedmissiles. The missile dynamics 40 contains a control section whichreceives the outputs of coders 37 and 38 and converts it into guidancecontrol for the guidance section of missile dynamics 40. The guidancesection then causes the missile to fly into and to stay in the line ofsight of the detector 13, and therefore, in the line of sight oftelescope 15. This will, of course, send the missile to the target 3.

An embodiment of the invention which is preferred has been chosen forpurposes of illustration and description only. The preferred embodimentillustrated is not intended to be exhaustive nor to limit the inventionto the precise form disclosed. It is chosen and described in order tobest explain the principles of the invention and their application inpractical use to thereby enable others skilled in the art to bestutilize the invention in various embodiments and modifications as arebest adapted to the particular use contemplated. It will be apparent tothose skilled in the art that changes may be made in the form of theapparatus disclosed without departing from the spirit of the inventionas set forth in the disclosure, and that in some cases certain featuresof the invention may sometimes be used to advantage without acorresponding use of other features. It is therefore to be understoodthat within the scope of the appended claims the invention may bepracticed otherwise than as specifically described. Accordingly, it isdesired that the scope of the invention be limited only by the appendedclaims.

We claim:

1. A missile guidance system comprising a radiant energy detector unithaving a reference axis; a missile having a radiant energy source andmissile control means; said detector unit being so constructed as todetect the polar position and the azimuth and elevation coordinates ofthe radiant energy source with respect to said axis and to present atits output a carrier wave which is frequency modulated to represent thepolar position of the missile; first means connected to said detectorunits output so as to have a signal output representative of saiddetected position; second means connected to an output of said firstmeans so as to have error signal outputs representative of error polarposition of the radiant source (and, therefore, the azimuth andelevation coordinates of the missile); third means having inputsconnected to the outputs of said second means for transferring saiderror position to the control means of said missile, wherein saidcontrol means controls the guidance of the missile to bring the missileinto line with the axis of the radiant energy detector; first and secondbias source means; said first bias means being connected to an input ofsaid third means so as to bias the azimuth coordinate; and said secondbias means being connected to another input of said third means so tobias the elevation coordinate.

2. A guidance system as set forth in claim 1, wherein said second meanscomprises a demodulator connected to the output of the first means; areference signal having a frequency output equal to the frequency outputof said demodulator; a comparison network; and wherein said referencesignal has a voltage and phase related to that of an output of saiddemodulator such that said comparison network-which has said referencesignal and said output of the demodulator as its inputs-produces saidcoordinates outputs of said second means.

3. A guidance system as set forth in claim 2, further comprising acontrol assembly having a stock means; telescope means and said detectorunit being connected to and aligned with said stock means; and saidtelescope having a sighting axis which is in substantial alignment withthe reference axis of said detector unit.

References Cited RODNEY D. BENNETT, Primary Examiner.

BENJAMIN A. BORCHELT, SAMUEL FEINBERG,

Examiners. M. F. HUBLER, Assistant Examiner.

1. A MISSILE GUIDANCE SYSTEM COMPRISING A RADIANT ENERGY DETECTOR UNITHAVING A REFERENCE AXIS; A MISSILE HAVING A RADIANT ENERGY SOURCE ANDMISSILE CONTROL MEANS; SAID DETECTOR UNIT BEING SO CONSTRUCTED AS TODETECT THE POLAR POSITION AND THE AZIMUTH AND ELEVATION COORDINATES OFTHE RADIANT ENERGY SOURCE WITH RESPECT TO SAID AXIS AND TO PRESENT ATITS OUTPUT A CARRIER WAVE WHICH IS FREQUENCY MODULATED TO REPRESENT THEPOLAR POSITION OF THE MISSILE; FIRST MEANS CONNECTED TO SAID DETECTORUNIT''S OUTPUT SO AS TO HAVE A SIGNAL OUTPUT REPRESENTATIVE OF SAIDDETECTED POSITION; SECOND MEANS CONNECTED TO AN OUTPUTS OF SAID FIRSTMEANS SO AS TO HAVE ERROR SIGNAL OUTPUTS REPRESENTATIVE OF ERROR POLARPOSITION OF THE RADIANT SOURCE (AND, THEREFORE, THE AZIMUTH ANDELEVATION COORDINATES OF THE MISSILE); THIRD MEANS HAVING INPUTSCONNECTED TO THE OUTPUTS OF SAID SECOND MEANS FOR TRANSFERRING SAIDERROR POSITION TO THE CONTROL MEANS OF SAID MISSILE, WHEREIN SAIDCONTROL MEANS CONTROLS THE GUIDANCE OF THE MISSILE TO BRING THE MISSILEINTO LINE WITH THE AXIS OF THE RADIANT ENERGY DETECTOR; FIRST AND SECONDBIAS SOURCE MEANS; SAID FIRST BIAS MEANS BEING CONNECTED TO AN INPUT OFSAID THIRD MEANS SO AS TO BIAS THE AZIMUTH COORDINATE; AND SAID SECONDBIAS MEANS BEING CONNECTED TO ANOTHER INPUT OF SAID THIRD MEANS SO TOBIAS THE ELEVATION COORDINATE.